luciuswillson,
Hi and WOW I am in the same boat. I got a started 4 star with a Saito 91 but I sold the Siato off for the $ reason. I went with a Supertiger 91. The 75 if you can get a deal would be fine.
I really think the lower weight 2 cycles are better for this plane. "Lighter is always better" works for me. Tower had 91 SuperTigers on sale for 125ish so look around, sale season is here.
Honestly I wanted to keep the Saito but I can buy 2 great 2 strokes for the same $.

Are you doing any MODS to your Four Star? I want to reduce the dihedral 50%, increase the rudder by 1/4", sheet the turttle deck with 1/32 ply and trim the canopy slightly smaller. Oh I always add a tank hatch. Many clip a bay off each end but I prefer not. I like them gracefull